Area Forecast Discussion
Issued by NWS Riverton, WY

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031
FXUS65 KRIW 140553
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1053 PM MST Fri Jan 13 2017

.Short Term...Tonight Through Monday

Dry and cold high pressure will be over western and central
Wyoming through Monday. Temperatures will gradually warm but with
relatively light winds over the area...the snow covered valleys
and basins...these areas will warm the least.  Some southwest
wind will develop Sunday through Monday across the south and east
where the most warming is expected.

.Long Term...Monday Night Through Friday

Beginning of FCST, split flow beginning to be replaced by ridging
and N to NW flow aloft in advance of the next strong jet push
into/through the wrn CONUS. Current storm trajectories are now
taking an earlier and slightly more southern track than previous
forecast MR model runs. This will actually delay the onset of
precipitation into/across wrn WY until really later Wednesday as the
jet dives down the coastline to Baja by late Thursday. New
cyclogenesis is not then expected to begin in the lee of the
central/southern Rockies until Friday morning...with chances for
precipitation occurring east of the Divide in WY sometime later
Friday as the cyclone rapidly spins up into the Plains states.

Seasonal to seasonally cold highs/lows throughout the forecast
period with little wind until Tuesday morning in the Cody
foothills then across the wind corridor from Tuesday afternoon
through Thursday morning. High wind highlights now possible by
Tuesday afternoon or evening across both these locations. Then the
next weather system brushes the wrn FA later Wednesday night as
modest ridging flattens with the flow eventually turning SW as the
large developing trof over wrn CONUS digs swd and allows allows some
EPAC moisture back into wrn WY. A few winter highlights may be
possible by Wednesday night across west central/southwest WY...but
does not look as good as 24 to 48 hrs ago. A pattern change back to
a colder airmass still looks probable by weeks end...lasting through
that weekend. However, long range pattern trends look to have keep a
relatively progressive 4/5 wave pattern in place, so hopefully any
good cold snaps coming through the region will be of short duration.

&&

.Aviation.../06Z Issuance/

The Rock Springs terminal will likely observe IFR/LIFR conditions in
low stratus and/or fog through at least 18Z with airfield minimums a
good possibility. Elsewhere some fog will develop in the valleys,
but confidence is not high enough to prevail it any terminal.
Confidence is also low on timing of improving conditions at Rock
Springs Airport, but will go for around midday before possibly going
back down in fog in the early evening. Winds will be mainly light
across the entire area through the period.

&&

.Fire Weather...

Dry and cold high pressure will be over western and central
Wyoming through Monday. Temperatures will gradually warm but with
relatively light winds over the area...the snow covered valleys
and basins...these areas will warm the least.  Some southwest
wind will develop Sunday through Monday across the south and east
where the most warming is expected.  With cold air trapped in the
valleys and basins with increasing temperature inversions...mixing
will be limited and wind will be light combining for poor smoke
dispersal expected through Monday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

SHORT TERM...C.Baker
LONG TERM...Braun
AVIATION...Braun
FIRE WEATHER...C.Baker



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